1. Field of the Invention
The present invention is directed to Archimedean-type screws and, more particularly, to helical screw conveyors and helical combustion systems.
2. Description of the Related Art
An Archimedes screw consists of a helical element or screw rotatably mounted inside a close-fitting open-ended cylinder. One end of the cylinder is placed in water and the other end is inclined above the horizontal. As the screw is turned, the helical flight on the screw draws water into the cylinder and carries it to the upper end where the water is discharged.
The Archimedean principle is applied to modern devices for conveying bulk material and to machines for drilling and extraction, food processing, and irrigation. For example, U.S. Pat. No. 4,750,274 discloses a sludge-processing device that utilizes two screw conveyors mounted inside a heat exchanger housing. The screw conveyors are rotated by a motor assembly to pass a sludge mixture through the heat exchanger.
A simple screw conveyor design utilizes a single flight helically formed around a central shaft, with the pitch and angle of the flight determined by the intended use. Flexible screw conveyors or centerless auger conveyors utilize a spring steel or a stainless steel helix that is enclosed within a flexible plastic tube and driven by an electric motor. When the flexible screw is rotated, an exposed section of the screw feeds material into the tube where it is then propelled to the discharge end. Flexible and rigid screw conveyors may be combined to form multiple intake and discharge point systems that can convey bulk material over short to medium distances, feed multiple discharge points selectively, and generally move material vertically, horizontally, or at any angle over, under, or around obstructions.
Screw conveyors are particularly useful in the food, drug, agricultural, general industry, and mining industries where a fully contained, metered effect is required. Sophisticated control systems monitor and regulate in-feed hoppers, discharge chutes, and the routing of the material as required.